Lamarck, Jean-Baptiste de (1744–1829)

During the latter half of the 18th century, a handful of science-oriented enlightened thinkers took time and change seriously; they saw history in terms of process and progress. Jean-Baptiste de Lamarck extended this perspective to become the first serious evolutionist. He argued for the mutability of animal species over vast periods of time, in an age when most other naturalists still maintained the fixity of life forms on a planet held to be only several thousand years old. As an invertebrate paleontologist, he took the fossil record in the geological column as empirical evidence demonstrating the evolution of species, into life forms of increasing complexity and greater perfection, as seen in their preservation up through the rock strata. Lamarck presented this controversial view of organic history in his major work, Zoological Philosophy (1809). Lamarck's evolutionary interpretation of life was in sharp contrast to the one offered by the contemporary vertebrate paleontologist Georges Cuvier, who held that the fossil record (with its gaps) represented a history of periodic creations and extinctions. Cuvier's vision suggested a series of divine creations, each special creation eventually followed by worldwide extinction due to a planetwide catastrophe. Thus, Cuvier was not an evolutionist. However, Lamarck saw the biological continuity of species (without any extinctions) throughout organic history. Because evolution challenged the entrenched beliefs in the biblical story of Creation in the Book of Genesis, with its 6 days of Creation, religious naturalists were not open to Lamarck's new worldview, despite those ongoing discoveries in geology and paleontology that clearly supported an ancient earth and the mutability of species on it, respectively.

[Page 754]Lamarck held that spontaneous generation would explain the sudden appearance of the first forms of life on earth. But, the fossil evidence to the contrary, he needed to account for the evolution of species over considerable time. Lamarck offered two explanatory mechanisms: the inheritance of acquired characteristics through use and disuse, and a form of vitalism that manifested itself only in complex animals. Lamarck's famous but now notorious example to demonstrate his first explanation involves the evolutionary history of the giraffe. He held that, eons ago, short-necked giraffes fed on the leaves of eye-level trees. Over time, these trees continuously became taller. Consequently, in order to reach and eat the ever-higher leaves, the giraffes needed to constantly stretch their necks. This acquired characteristic of a longer neck (due to continuous stretching) was inherited by the offspring over numerous generations. The ongoing accumulation of this useful and specific characteristic has resulted in the long-necked giraffe of modern times.

Furthermore, Lamarck speculated that complex animals with consciousness could actually will those characteristics (structures and functions) that they needed or desired in order to adapt to, and survive in, changing environments; he even thought that, through willing, new organs and behavior patterns could emerge over time. Not surprisingly, because of a lack of convincing experimental evidence, naturalists have not accepted as true Lamarck's two explanatory mechanisms for the evolution of life on this planet.

Concerning the origin of our own species, Lamarck boldly claimed that the human animal had emerged from an orangutan-like primate somewhere in Asia. Through slow evolution, he maintained, our human species gradually acquired those mental faculties and biological characteristics it has today. Moreover, Lamarck argued that humans differ from the living apes and monkeys merely in degree rather than in kind; the superiority of human reason is grounded in the larger and more complex brain of our species. However, the present fossil record points to Africa as the cradle of humankind. Even so, modern primatology does clearly demonstrate the striking similarities between the human animal and the great apes.

...